Communication!!!! Discuss about all aspects of the app. Every day, all work needs to be discussed, and agreed on with the product owner. Every message text, edge case, color. Don’t assume anything. Or, assume, but also, confirm with the client. I can’t stress this enough.

Write test cases in parallel with the development. They need to be created every day, after each discussion with the client. After the development is ready, everybody knows what to test.

Make sure the stories have all the use cases described in them.

Start testing as early as possible. The problems will be discovered and addresses in a timely manner.

Follow the test cases when testing.

Have the design team look over the build on each feature implemented. Discuss and negotiate all the technically challenged design items so you don’t waste precious time on expendable features.